The invention relates to a system and a method for a system featuring an electromagnetic position detection system and an instrument of which the position is able to be determined in at least one electromagnetic field created with the electromagnetic position detection system, with a device distorting the electromagnetic field being located at least partly in the electromagnetic field or a device distorting the electromagnetic field being able to be brought at least partly into the electromagnetic field, and with the position of the instrument being determined taking into account the position of the device or of a part of the device in the electromagnet field and the distortion of the electromagnetic field associated with it.
